A couple of times in the past year or two I’ve pulled away towing my 28ft TT at about 6k lbs but realized several miles down the road that I failed to place it in Tow Haul mode. I thought to myself, hmm, I didn’t notice any difference in gaining speed nor any difficulty pulling until several miles down the road so I experimented a few times and realized a 1-2 mpg increase when leaving it in Standard mode rather than Tow Haul. Wondering if anyone has had a similar experience or has some input as to how this could be possible. All input appreciated.
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Standard/Regular mode vrs Tow/Haul mode, is this crazy?
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Not speaking for the Ford programming, but the Chevy/Gm programming tends to hold the shifts a bit longer going up and shifts faster on the down. On the up side (acceleration) this is done to assist in increasing line pressures to the trans resulting in a fit firmer more crisp shift between gears for clutch life. On the down side, it holds gears in some instances to avoid over shifting (excessive gear hunting) as the engine lugs slightly when say pulling a hill or small changes in speed, but may shift early in say a breaking situation to help with slowing the trailer.
Next time monitor loaded and unloaded shift points. I did a similar test in my 2500's (GM) by setting the cruise to 65 mph, then on acceleration resuming the set speed at say 25 mph and monitoring the up shift points in both RPM and MPH. I chose this method because the ECU performed in a repeatable manner each time during the 40mph speed increase.Joseph
Tow Vehicle: 2024 GMC K3500 Denali Ultimate Diesel
Coach: 303RLS Delivered March 5, 2021
South of Houston Texas
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Originally posted by Schiefswret View PostA couple of times in the past year or two I’ve pulled away towing my 28ft TT at about 6k lbs but realized several miles down the road that I failed to place it in Tow Haul mode. I thought to myself, hmm, I didn’t notice any difference in gaining speed nor any difficulty pulling until several miles down the road so I experimented a few times and realized a 1-2 mpg increase when leaving it in Standard mode rather than Tow Haul. Wondering if anyone has had a similar experience or has some input as to how this could be possible. All input appreciated.2018 Reflection 303rls
MORryde IS, FlexArmor roof
Blue Ox Super Ride hitch
2017 Ford F350 CCSB SRW
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Hi Dave,
With my Ecoboost F150, I always towed in Tow/Haul mode and in 5th gear. (6th locked out) This kept the engine at the low end of the boosted RPM range where it felt more comfortable and prevented downshifts on moderate grades.
With the diesel F350, I also set Tow/Haul but didn't like the 10-8 downshift so I locked out 10th gear. (9-8 is much more comfortable) Hauled about 1400 miles like this. (Ontario to Florida)
On the return trip, I did not use Tow/Haul but still didn't like the 10-8 downshift . . . so I locked out 10th again. I could not sense any difference in engine/transmission performance with or without Tow/Haul . . . but, this could be because the diesel has way more torque than needed for more-or-less level towing with an 11,000 lb trailer.
RobCate & Rob
(with Border Collies Molly & Angel + Kitties Hazel & Elsie)
2015 Reflection 303RLS
2022 F350 Diesel CC SB SRW Lariat
Bayham, Ontario, Canada
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Engineers don't always get it just right but tow haul is the best use of the powetrain for best performance. It's calibrated toward the high end of capacity where lighter loads would operate better with tow haul turned off. All the speed matching and downshifting to help save brakes makes tow haul a valuable feature to use.
Jim
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Originally posted by Schiefswret View PostA couple of times in the past year or two I’ve pulled away towing my 28ft TT at about 6k lbs but realized several miles down the road that I failed to place it in Tow Haul mode. I thought to myself, hmm, I didn’t notice any difference in gaining speed nor any difficulty pulling until several miles down the road so I experimented a few times and realized a 1-2 mpg increase when leaving it in Standard mode rather than Tow Haul. Wondering if anyone has had a similar experience or has some input as to how this could be possible. All input appreciated.
Dave2016 Reflection 27RL
2015 Silverado 2500HD 6L
B&W Patriot 18k slider
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Originally posted by Cate&Rob View PostWith the diesel F350, I also set Tow/Haul but didn't like the 10-8 downshift so I locked out 10th gear. (9-8 is much more comfortable) Hauled about 1400 miles like this. (Ontario to Florida)On the return trip, I did not use Tow/Haul but still didn't like the 10-8 downshift . . . so I locked out 10th again. I could not sense any difference in engine/transmission performance with or without Tow/Haul . . ...Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.
Howard & Francine
2017 Ford F-350 DRW, '19 315RLTSPlus
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It's a balance. I will use regular mode in the campground to force an upshift to keep the noise down. Using tow haul on some hills I'll throttle past the cruise setpoint to force an upshift as well so the shift maps while being good are not always perfect. My father's E350 will never upshift unless you back off the throttle then tip back in where it will hold in the next gear. No tow haul used on his rig. Poor trans calibration at best, but the 5.4 gets good mileage.
Jim
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Originally posted by howson View Post
Did you happen to compare fuel mileage?
10.5 MPG Ontario to Florida. (Early February)
12.5 MPG Florida to Ontario. (Late March)
I attribute the much better mileage on the second trip to warmer temps and the Diesel engine being more broken in.
There may have been a small contribution by not selecting Tow/Haul . . . but I could not feel a difference and most of the miles are steady state 9th gear.
Rob
Cate & Rob
(with Border Collies Molly & Angel + Kitties Hazel & Elsie)
2015 Reflection 303RLS
2022 F350 Diesel CC SB SRW Lariat
Bayham, Ontario, Canada
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Everyone knows its downhill all the way from Florida to Ontario. Seriously, though, I use tow/haul for acceleration, I usually tow at 62 or 63 mph with cruise control on level or mostly level interstates. At that speed, I disengage tow/haul to enable an upshift to 6th gear, which otherwise wouldn't happen until 66 mph. I never use cruise on hilly terrain, and if I need to cancel the cruise I re-engage tow/haul. I also use the manual mode of the transmission when descending steep grades, and shift proactively as needed (truck driver in previous life). I feel the cruise + exhaust brake over revs the engine on some downgrades. Selecting the manual mode prevents this. Fuel economy can dip under 8 in mountainous areas, can be as good as near 11 if it is all flat. On a long trip, I use the trip B for fuel economy number from when we leave home to when we return. Trip A I reset at each full fillup. Last year's Bakersfield to Minnesota round trip of 5600 miles, we got 10.7 for the trip.Dave and Darren Bakersfield, CA
2019 GMC Denali dually 4x4 duramax, BW puck hitch, timbrens
2015 Chevrolet 3500 CC duramax SB SRW (much loved; replaced with dually)
2021 Solitude 390 RK-R (3 A/C, solar, gen, 8K axles DP glass), comfort ride shocks, VIN 03584
Max and Riley, our chihuahua/jack russell furbabies
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